Is the question confusing?
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For the original question, perhaps I'm missing something, but when I read the question, I didn't understand it to mean that not everything is going to end up back in the original proportion. I spent a long time going on a wild goose chase looking for how much you'd have to add to get everything back into the original proportions. I understand now after watching the explanations, but perhaps providing a hint that addresses that or rewording it slightly would be helpful.